Cenomanian Turonian Research Articles

Seismic characterization of Cenomanian–Turonian carbonate platform based on sedimentological and geophysical investigation of onshore analogue outcrop (northern Lebanon)

AbstractOutcrop analogues play a key role in the characterization of subsurface carbonate platforms. The lack of well data and relevant outcrop analogues can result in the misinterpretation of seismic data. To address this issue, we apply an integrated workflow based on sedimentology, geophysics and petrophysics on outcrop analogues present onshore Lebanon, to constrain the carbonate platform's properties on onshore seismic data. A thorough sedimentary description is completed for a 400‐m‐thick Cenomanian–Turonian carbonate platform located in Kfarhelda, northern Lebanon. P‐wave velocity is acquired directly on the outcrop, and the petrophysical properties are measured on 44 samples. A 1D synthetic seismogram is computed with Ricker wavelet 25 Hz resembling seismic resolution. The resulting reflectors are mainly (1) high amplitude reflectors at the limit between two facies with contrasting physical properties enhanced by diagenesis, (2) moderate amplitude reflectors corresponding to stratigraphic limits at the transition between facies and (3) very low amplitude reflectors in karstified units. The integration of outcrop and seismic data is based on the generation of the synthetic seismogram to identify the geological origin of reflectors. The best fit between the synthetic seismic and seismic profile is used to interpret a seismic facies representing bedded limestones of Sannine and Maameltain formations (Cenomanian–Turonian). Two other distinctive reflectors are identified at the boundary of the Marly Limestone Zone, and the Channel facies unit characterized by bioclastic packstone to floatstone. This study highlights the importance of using outcrop analogues to identify the seismic signal of stratigraphic sequences and improve the interpretation of onshore seismic data.

UPPER CRETACEOUS FORAMINIFERA MURGEINA APULA (LUPERTO SINNI, 1968): A METHUSALEM AND CENOMANIAN-TURONIAN BOUNDARY SURVIVOR TAXON

The benthic foraminifera Murgeina apula (Luperto Sinni), originally described as Nummofallotia apula from the Upper Cretaceous of southern Italy, represents a common taxon in the middle-upper Cenomanian Sarvak Formation of southwestern Iran as well as the Campanian-early Maastrichtian of Croatia. The specific identity of the Iranian and Italian as well as Croatian specimens is confirmed by equivalent biometric data and identical test structure. The agglutinated wall (inner part) of M. apula excludes its assignment to the porcelaneous Nummofallotia Barrier & Neumann. Nummofallotia is currently placed in the family Meandropsinidae Henson, while for Murgeina with its bilamellar wall inclusion in the Ventrolaminidae Weynschenk is favoured. Nummofallotia cenomana Luperto Sinnni, described from the Cenomanian of southern Italy and lacking any hard facts for species discrimination (e.g., dimensions, inner structure) is herein considered tentatively a junior synonym of Murgeina apula requiring re-examination of the type-material. M. apula represents another survivor of the Cenomanian–Turonian boundary extinction event and, with a long stratigraphic range from the middle Cenomanian to the (early) Maastrichtian, is similar to another Methusalem taxon such as Moncharmontia apenninica (De Castro) with a comparable range.

Biodiversity of †pycnodonts (Actinopterygii) during the Cenomanian–Turonian (Upper Cretaceous)

ABSTRACT By comparing the morphological variability of two groups of pycnodonts, the Coccodontoidea and the Nursalliini, the author demonstrates that in the Late Cretaceous these two groups had adopted completely different blauplans. Throughout the Cretaceous and the Eocene, the Nursalliini maintained the typical shape of the pycnodonts, rounded and flattened. The Cocodontoidea expressed 21 new species that belonged to 17 new genera, across which there was extraordinary biodiversity. The typical body plan was almost abandoned, and elongated, and somewhat very tapered, forms emerged (Stenoprotome), which lived alongside very short and very high fish. Indeed, this period produced the shortest and the highest fish that have ever lived (Maraldichthys). Indeed, while the more highly variable groups (Coccodontoidea) represented a punctiform episode in the evolutionary history of pycnodonts, remaining confined to the arm of Tethys (central Lebanon) and to the time period corresponding to the lower upper Cenomanian, the morphologically more conservative groups (Nursalliini) colonised the seas of the entire planet from the Cretaceous to the Eocene, even surviving the great mass extinction period corresponding to the Mesozoic-Cenozoic passage. Thus, the enormous biodiversity of Coccodointoidea did not represent a selective advantage over the environmental crisis at the end of the Cretaceous.

Depositional and diagenetic controls on reservoir properties along the shallow-marine carbonates of the Sarvak Formation, Zagros Basin: Petrographic, petrophysical, and geochemical evidence

As the second important oil reservoir of Iran, shallow-marine carbonates of the Sarvak Formation were deposited in a tectonically active setting, under a warm and humid paleoclimatic condition. This study focuses on sedimentological, geochemical, and petrophysical analysis of this formation in the Abadan Plain, Zagros Basin. Petrographic studies have resulted in the recognition of five microfacies deposited in lagoon, patch-reefs and their taluses, shoal, and open marine environments. They represent a ramp-like depositional model for the Sarvak Formation. Two third-order depositional sequences are differentiated and dated as Cenomanian–Turonian, according to the results of biostratigraphic analysis. Effects of intensive meteoric diagenesis are recorded beneath the two paleoexposure surfaces (Cenomanian–Turonian boundary, and middle Turonian). They include pervasive dissolution (karstification), collapsed brecciation, silicification, recrystallization, and development of paleosols. Additionally, decreased values of δ18Ocarb and δ13Ccarb and a sharp inverted-J pattern in the δ18Ocarb vs. δ13Ccarb cross plot indicate major meteoric phases. The most decreased values of δ18Ocarb (−7 ‰) and δ13Ccarb (−8.6 ‰) are measured from the meteoric cements and paleosols. Reservoir quality evaluation revealed that the best reservoir zones of the Sarvak Formation are developed within the rudist-dominated facies with intensive meteoric dissolution. They are concentrated within the regressive systems tract of the Cenomanian sequence. Fractured and dolomitized mud-dominated facies provided the speed/baffle zones in transgressive systems tracts, and highly compacted/cemented facies formed the barrier units. It could be concluded that the facies characteristics and meteoric diagenetic processes had major controls on reservoir quality of the Sarvak Formation, in the Abadan Plain. These controlling factors are predictable in a high-resolution sequence stratigraphic framework.

A first high-resolution carbon isotope stratigraphy from the Boreal (NW Germany) for the Berriasian to Coniacian interval—implications for the timing of the Aptian–Albian boundary

High-amplitude changes in sedimentary δ13C characterize the Cretaceous system and have been proven useful for supra-regional chemostratigraphic correlation. In the Cretaceous, these δ13C perturbations indicate large shifts between the global carbon reservoirs that are usually caused by volcanic activity of large igneous provinces, the widespread deposition of thick organic carbon-rich sequences and/or changes in orbital parameters. Here, we present an upper Berriasian to lower Coniacian (c. 142–88 Ma) composite carbon isotope record based on 14 drill cores, 2 outcrops, and almost 5,000 samples. The total record comprises a composite thickness of more than 1,500 m. All cores and successions are located in the larger Hanover area, which represents the depocenter of the North German Lower Saxony Basin in Early to mid-Cretaceous times. In Northern Germany, Boreal Lower Cretaceous sediments are predominantly represented by CaCO3-poor mud and siltstones of up to 2,000 m thickness, which become more carbonate-rich during the Albian–Cenomanian transition and even chalkier in the upper Cenomanian to Coniacian interval. The carbon isotope record reveals a number of global key events, including the Valanginian Weissert Event, the Oceanic Anoxic Events (OAEs) 1a and d, and the Kilian Event (Aptian–Albian boundary, part of OAE 1b). For the early Late Cretaceous, the Mid-Cenomanian Event, the OAE 2 (Cenomanian–Turonian Boundary Event), and the Navigation Event, among others, have been identified. The Kilian Event represents the Aptian–Albian boundary and has been identified herein for the first time in Northern Europe. Based on the evaluation of its relative position to the Vöhrum boundary tuff, we tentatively propose a slightly older age for the Aptian–Albian boundary of c. 113.65 Ma instead of 113.2 Ma. The observed chemostratigraphic events enable a detailed stratigraphic comparison with Tethyan and other Boreal records and associated paleoenvironmental data. Thus, this new detailed chemostratigraphy provides a unique opportunity to potentially overcome many still existing Boreal–Tethyan correlation issues. The presented record can be considered almost complete, albeit a 2-Myr gap during the early Albian is likely, and condensed intervals occur specifically during the lower Aptian.

Late Cretaceous radiolarians from the Noni Formation, West Timor, Indonesia

Late Cretaceous (Cenomanian–Turonian) radiolarian fauna was recovered from a single chert sample of the Noni Formation in the Miomaffo District of West Timor, which is generally viewed as part of the allochthonous ‘Banda Terrane’. This fauna is characterized by the presence of Cryptamphorella conara, Diacantocapsa euganea, Dictyomitra formosa, Dictyomitra montisserei, Guttacapsa biacuta, Stichomitra communis, Patelula verteroensis, Pessagnobrachia fabianii, Praeconocaryomma lipmanae and others. The character of the radiolarian fauna shows a close resemblance to those in South Sulawesi and is very different from age-equivalent radiolarian faunas in the ‘autochthonous’ southern foldbelts of West Timor (Kolbano) and Timor Leste (Viqueque). This report on the Late Cretaceous radiolarians in Timor attempts to identify the fauna, to clarify its age, and to indicate the paleogeographic origin of radiolarian-bearing chert of the Noni Formation.

Pliosaurid (Reptilia: Sauropterygia) remains from the Upper Cretaceous of Japan, and their biostratigraphic and paleogeographic significance

Four indeterminate pliosaurid remains from the Cenomanian and Turonian of the Yezo Group in Hokkaido, northern Japan, are described/re-described. Although their fragmentary nature does not allow identification to lower taxonomic levels, two specimens represent large individuals whose skull size approaches that of Megacephalosaurus from North America. The late Turonian age of the youngest specimen indicates that the Pliosauridae survived in the northwestern Pacific to least the time when the entire clade was nearing extinction. Along with the known stratigraphic distributions of the Elasmosauridae and Polycotylidae in the Japanese Cretaceous, the described pliosaurid specimens demonstrate that all three major plesiosaurian clades of the Late Cretaceous crossed the Cenomanian–Turonian boundary at least in this region.

Taxonomic Diversity of Cenomanian–Turonian Dinocysts in the Northern Hemisphere: Some Aspects of Paleobiogeography and Paleoclimatology

Taxonomic Diversity of Cenomanian–Turonian Dinocysts in the Northern Hemisphere: Some Aspects of Paleobiogeography and Paleoclimatology

Oyster-dominated macrobenthic associations in the Cenomanian of Djebel Bouarif (Aures Mountains, Northeastern Algeria)

In the Batna area of Algeria, the Cenomanian is represented by the Smail Marls Formation, a highly fossiliferous unit with a diverse benthic macrofauna (mainly of ostreid bivalves). A total of 1090 specimens belonging to 65 macrobenthic species were identified from 19 stratigraphic samples. The macrofaunal communities were quantitively analyzed using the hierarchical clustering (HC), nonmetric multidimensional scaling (NMDS), and permutational analysis of variance (PERMANOVA). Five distinct associations are recognized: 1) Costagyra olisiponensis, 2) Rhynchostreon suborbiculatum, 3) Aspidiscus cristatus, 4) Rhynchostreon suborbiculatum-Mecaster ameliae, and 5) Pycnodonte vesicularis. Data suggests that during the Cenomanian, the dominance of high-energy opportunistic oyster species within the soft marly sediments are related to their adaptive strategies. The changes noted in the community structure are attributed to sea-level fluctuations, rate of sedimentation and the prevailing hydrodynamics. Towards the uppermost Cenomanian and the Cenomanian–Turonian boundary, the oysters become rare due to eustatic sea-level rise and this decline coincides with increasing predation intensity on oysters and the destruction of their shallower habitats.

Paleoenvironmental significance of the carbon isotope record across the Cenomanian–Turonian transition and the Oceanic Anoxic Event 2 (OAE2) in the southeastern Neotethys, Zagros, Iran

A high–resolution carbon isotope record of pelagic carbonates (δ13Ccarb) from the Zagros Mountains, Iran, documents a 1.8‰ positive carbon isotope excursion (CIE) in the southeastern Neotethys during the Cenomanian–Turonian transition, corresponding to Ocean Anoxic Event (OAE2). The succession is controlled by biostratigraphy that includes the Rotalipora cushmani, Whiteinella archaeocretacea, and Helvetoglobotruncana helvetica biozones. The CIE is characterized by a positive shift culminating in a first positive peak (at 3.3‰), followed by a 1‰ negative excursion, accompanied by the highest δ18Ocarb values that can be interpreted as the result of a short–lived global cooling, the Plenus Cold Event. A subsequent second positive peak and a plateau of higher δ18Ocarb values are followed by relatively low values in the earliest Turonian akin to pre–excursion values. The biostratigraphic positions of the three diagnostic maximum points, referred to as peaks A, B, and C, within the generally positive CIE indicate a synchronous δ13Ccarb variability worldwide. The average δ13Ccarb values in southeastern Neotethys are generally lower compared to the open–ocean records of the same period. We attribute this offset to a substantial regional regression combined with recycling of isotopically light organic carbon. The diachronous deposition of black shales/mudstones after the onset of positive CIE suggests that its formation strongly depends on local paleogeography and paleoenvironmental factors.

Chemostratigraphy of the lower Danubian Cretaceous Group (Cenomanian–lower Turonian, Bavaria, SE Germany)—A new carbon isotope reference curve and inter-basinal correlation

Core section KB 06-2020, drilled north of Regensburg (SE Germany), covering the lower Danubian Cretaceous Group, has been logged in detail and sampled for chemostratigraphic investigation throughout the Cenomanian–lower Turonian. Resting unconformably on Upper Jurassic carbonates, the succession includes the Regensburg (lower Cenomanian–middle upper Cenomanian), the Eibrunn (Cenomanian–Turonian boundary interval), the Winzerberg (lower Turonian; Reinhausen and Knollensand members) and the Kagerhöh formations (middle Turonian, Eisbuckel and Pulverturm members only). The correlation of carbon stable-isotope trends from core section KB 06-2020 with the expanded Dover section (southern England) and the Bad Abbach section (south of Regensburg) provides evidence for a diachronous, NE-directed onlap of the Cretaceous strata onto the Bohemian Massif. Several Cenomanian carbon isotope events have been recognised (Mid-dixoni, P/B Break, Monument as well as the b1 and b2 peaks) while the selective absence of events above conspicuous sedimentary unconformities provides evidence for stratigraphic gaps associated with sea-level falls. A significant positive carbon isotope excursion in the Cenomanian–Turonian boundary interval, Oceanic Anoxic Event 2 (OAE 2), has been recorded in the Eibrunn Formation. Correlation with the European reference section from Eastbourne (southern England), Pont d'Issole (southern France), and the regional Grub section provides evidence of a rather complete development of OAE 2 in the Danubian Cretaceous Basin. The δ13C curve obtained from core section KB 06-2020 is proposed as a regional reference curve. Additionally, the Plenus Cold Event (PCE) is recognisable in the oxygen stable-isotope data.

Cretaceous southern high latitude benthic foraminiferal assemblages during OAE 2 at IODP Site U1516, Mentelle Basin, Indian Ocean

At Site U1516 (Mentelle Basin, southeast Indian Ocean, offshore western Australia), the International Ocean Discovery Program (IODP) Expedition 369 recovered an almost complete pelagic record of the Upper Cretaceous, including the Oceanic Anoxic Event 2 (OAE 2). To better understand paleoenvironmental changes across OAE 2, 32 samples were analysed for benthic foraminiferal abundance data that represent one of the few benthic foraminiferal datasets spanning the OAE 2 in the southern high latitudes.The OAE 2 interval at Site U1516 is characterized by an interval of low CaCO3 content that contains a prominent positive Carbon Isotope Excursion (CIE). The record of the OAE 2 can be subdivided in pre OAE 2, pre max-CIE, low CaCO3, and post low CaCO3 intervals. Through the Cenomanian–Turonian boundary, we document an extreme decline in benthic foraminifera during OAE 2, that is followed by a profound repopulation event in the post low CaCO3 interval.Benthic foraminiferal assemblages indicate an outer neritic to upper bathyal depositional environment. During the pre OAE 2 and pre max-CIE intervals, calcareous deep-water gavelinellids, lingulogavelinellids and gyroidinids are dominant. In the low-carbonate interval, the microfossil record documents a substantial increase in radiolaria and foraminifera are almost absent as only three out of nine samples contain benthic foraminifera. Changes in benthic foraminiferal assemblage composition are documented in the initial low CaCO3 interval, underlying the maximum CIE and associated interferences. Comparison of the pre- and post-CIE benthic foraminiferal assemblages highlights a distinct repopulation event during the post max- CIE interval mainly represented by the conspicuous increase in abundance of agglutinated taxa and Conorboides. Compared to other southern high latitude records, the dataset collected at Site U1516 represents one of the most complete benthic foraminiferal records across the OAE 2 that registers the Late Cretaceous environmental changes in the Southern Hemisphere.

Stratigraphy, palaeontology and sedimentology of the Upper Cretaceous of northern Tademait (Sahara, Algeria)

Thorough sedimentological and palaeontological analyses of four expanded Upper Cretaceous sections in northern Tademait had allowed us to address and reconsider the stratigraphical framework of the so-called ‘Continental Intercalary’ and ‘Hamada series’ in this remote Saharan area. These four sections (i.e., Meguidene, Gara Samani, Oued El Mezaourou-Gour Louazouaza, and El Menia) document Upper Cretaceous strata overlying post-Palaeozoic substrata and ranging from the clastic Gara Samani Formation (of supposed early Cenomanian age), through the El Golea Clays (lower–middle Cenomanian), the Gour Louazouaza Formation (lowermost upper Cenomanian, with the Oued El Mezaourou Limestone Member ranging from the Neolobites vibrayeanus to the Vascoceras gamai ammonite zones of the uppermost Cenomanian, and the Marls of Gara Mta El Mar Member of the Choffaticeras sinaiticum ammonite Zone in the lower, but not lowermost, Turonian), to the Ain El-Hadjaj Formation (of alleged Campanian age). Most efforts have concentrated on the ‘mid’-Cretaceous deposits that yield vertebrates and diversified ammonite and macrofossil assemblages. In spite of these improved correlations, further bio-chronostratigraphical data are needed in order to constrain the stratigraphical gap within the Gour Louazouaza Formation at the Cenomanian–Turonian boundary (C/TB) better. The succession studied can be correlated with other similar-aged sections in North Africa and illustrates the development of braided fluvial and aeolian dune-interdune environments followed by a ramp depositional system in response to the early Late Cretaceous second-order sea level rise along the southern margin of the Tethys.

Northernmost occurrences of plesiosaurs and turtles in the Upper Cretaceous of Eurasia

Here we describe the first findings of reptile remains in the Upper Cretaceous marine strata of Siberia, which represent the northernmost occurrences of plesiosaurians, ?mosasaurids and turtles in the Cretaceous of Eurasia (66–72° N palaeolatitudes). The specimens come from the upper Cenomanian, Turonian and Coniacian of the Pyasina River basin, Santonian and Maastrichtian of the Tanama River and upper Santonian–lower Campanian of the Kheta River. They include remains of polycotylid and elasmosaurid plesiosaurians, as well as indeterminate small and osteologically immature plesiosaurians, indicating a somewhat typical Late Cretaceous plesiosaurian assemblage at the Arctic Polar Circle and implying that these shallow-water regions possibly used by plesiosaurians as a birth and nursery areas during the polar summer. In addition to plesiosaurian remains, a partial carinate ?mosasaurid tooth, and two turtle shell fragments, assigned to either non-marine Macrobaenidae or to marine Chelonioidea, and to non-marine Testudinoidea, are discovered, providing first direct evidence for the presence of these reptile groups in the Late Cretaceous of Northern Siberia. The findings of turtles are the northern most records of this group in the Cenomanian and Coniacian of Eurasia, which parallels previous records from the upper Cenomanian of Arctic Canada, and further supports warm climate conditions during the Cretaceous Greenhouse at high latitudes. Therefore, the Cenomanian–Turonian Boundary Event associated to the climate warming and to the beginning of the Cretaceous thermal maximum is well-recognized in Northern Siberia showing an expression of this “global” event over the Arctic region.

Redox conditions and ecological resilience during Oceanic Anoxic Event 2 in the Western Interior Seaway

Oceanic Anoxic Events (OAEs) are important geological events that may be analogues to future climate-driven deoxygenation of our oceans. Much of the global ocean experienced anoxic conditions during the Cenomanian–Turonian OAE (OAE2; ∼94 Ma), whereas the Western Interior Seaway (WIS) experienced oxygenation at this time. Here, organic geochemical and palynological data generated from Cenomanian–Turonian age sediments from five sites in the WIS are used to investigate changing redox and ecological conditions across differing palaeoenvironments and palaeolatitudes. Heterogeneity across the sites is apparent, but important relationships and trends among oceanographic variables are recognised: 1) Increasing total organic carbon (TOC) and CaCO3 percentages indicate the onset of a sea-level maximum towards the end of OAE2; 2) C28 sterane is shown to be a useful marker for prasinophyte abundance, and concurrent increases in this marker and overall sterane abundance indicate prasinophyte-driven increase in algal productivity in a stratified water column; and 3) sterane ratios can be a more reliable geochemical proxy than redox proxies for assessing the Benthic Oxic Zone. Our redox data do not always follow established trends for the WIS overall, particularly for proximal settings. We therefore surmise that local effects, such as nutrient-driven expansion of the oxygen minimum zone and/or sedimentation-driven anoxia just below the sediment-water interface, have overprinted regional trends.

Regional conditions cause contrasting behaviour in U-isotope fractionation in black shales: Constraints for global ocean palaeo-redox reconstructions

The U-isotope system is a well-established palaeo-redox proxy that potentially constrains the global extent of marine anoxia during average as well as extreme redox events throughout Earth's history. A typical archive that forms underneath a reducing water column and acts as an intense U sink is organic-rich black shale. However, the degree to which black shale archives reflect the marine U-isotope signature is not well understood because U-isotope fractionation between U(VI)-bearing seawater and U(IV)-bearing black shales may vary as a function of local environmental conditions. Here, we present a combination of U-isotope and elemental concentration datasets, supported by a complementary Mo-isotope record, for the Furlo sedimentary section in Marche–Umbria, Italy and interrogate the combined systematics to unravel the mechanisms controlling the U-isotope fractionation factor between black shales and ambient seawater. We examine black shales deposited before and during Oceanic Anoxic Event 2 (OAE 2), which was one of the most extreme climatic perturbations of the Mesozoic Era that took place around the Cenomanian–Turonian boundary (Late Cretaceous, c. 94 Ma). The results of this study show that the U-isotope signature in the black shales deposited before OAE 2 was controlled by different mechanisms than the U-isotope ratios recorded in black shales deposited during OAE 2, with both stratigraphic intervals likely influenced by local environmental conditions. Probable local environmental changes include increased U reduction associated with biomass at or above the sediment–water interface and varying dissolved hydrogen sulphide concentrations in the water column and sediment. The overall results of this study confirm that black shales are a highly complex archive for U-isotope studies of past oceanic redox conditions, due to the sensitivity of the U-isotope fractionation mechanism to local environmental conditions, which are difficult to constrain. We propose the application of a ∆238Ushale-seawater of 0.6 ± 0.1 ‰ to black shale records deposited under locally constant euxinic conditions at non-restricted settings.

Impacts of Depositional Facies and Diagenesis on Reservoir Quality: A Case Study from the Rudist‐bearing Sarvak Formation, Abadan Plain, SW Iran

AbstractAn integrated geological‐petrophysical analysis of the rudist‐bearing sequence of the Cretaceous Sarvak Formation is given one giant oilfield, and provides an improved understanding of this main reservoir in the Abadan Plain, in the Zagros Basin, SW Iran. The main objective of this study is to evaluate reservoir potential of the Sarvak Formation, and then to utilize the calibrated well log signature to correlate reservoir potential in un‐cored wells. Eight main facies are recognized and categorized in five facies groups: lagoon, shoal, rudist‐biostrome, slope, and shallow open marine, deposited on a shelf carbonate platform. Given the distribution of diagenetic products and their effects on pore systems, three diagenetic facies namely, (DF‐1) low dissolution and cementation; (DF‐2); high dissolution; and (DF‐3) high cementation are differentiated. The initial sedimentary characteristics in combination with distribution of diagenetic products play an important role in reservoir quality heterogeneity. The effect of diagenetic processes related to disconformities mainly depends on the facies nature below these surfaces. Grain‐dominated facies of shoal and rudist debris, observed below the Cenomanian–Turonian disconformity, are mostly characterized by high dissolution and interconnected pore systems. Finally, depositional and diagenetic facies in the studied wells are correlated by petrophysical well log data, leading to distribution of the reservoir zones. Data obtained can be utilized for efficient reservoir characterization of the Sarvak Formation and its equivalent units in the Arabian Plate.

A new record of the Cenomanian–Turonian transgression preserved in the Ikorfat Fault zone, Nuussuaq Basin, West Greenland

The Ikorfat Fault zone in northern Nuussuaq, Central West Greenland, has preserved a hitherto unknown succession of Upper Cretaceous marine mudstones referred to the Itilli Formation, which have been removed by erosion on the footwall block and buried deeply below sea-level on the hanging-wall block. Outcrops in the fault zone provide new data on sedimentology, palynology, stable carbon isotopes and organic geochemistry in the lower part of the Itilli Formation. A new, detailed geological map of the study area is based on digital photogrammetry. Marine organic walled dinoflagellate cysts (dinocysts) demonstrate a late Cenomanian–Turonian age, coeval with the Oceanic Anoxic Event 2 (OAE2) and link the Nuussuaq Basin with the Baffin Bay and Sverdrup Basins. The Ikorfat Fault zone is part of the eastern boundary fault of the Nuussuaq Basin. Lower Campanian listric faults truncate the footwall block. Subsidence along steep normal faults continued during deposition of the volcanic Vaigat Formation of Danian to Selandian age. The downthrow of the hanging-wall block was around 2.5 km.

Timing of the Greenhorn transgression and OAE2 in Central Utah using CA-TIMS U-Pb zircon dating

Contextualizing subbasinal influences on accommodation and pace of the rapid landscape evolution during the base-level rise of the Upper Cretaceous (upper Cenomanian–lower Turonian) Greenhorn Cycle within the Western Interior of North America requires refined stratigraphic controls of key sediment successions. Herein, a blended analysis of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), chemical abrasion thermal ionization mass spectrometry (CA-TIMS), and δ13C isotopic data is utilized to identify two regionally significant ash-fall marker beds southeast of the Wasatch Plateau, specifically the TT1 and TT4, which bracket the Cenomanian–Turonian boundary and the Greenhorn Cycle transgression in the Western Interior Seaway (WIS). Based on our analysis of the recovered ash-fall zircons, a meaningful depositional age (DA) for the TT1 is 94.616 Ma ± 0.027 and 94.010 Ma ± 0.017 for the TT4 bentonite of the Tununk Shale.When coupled with the pre-existing biostratigraphic framework, correlation potential greatly increases with the (TT1) Naturita falling within the Sciponoceras gracile Assemblage Zone. Common molluscs associated with this biozone within the southern and central regions of Utah include Inoceramus pictus, Euomphaloceras spp., and Pycnodonte newberryi. The (TT4) Tununk within the upper portion of the Watinoceras coloradoense Assemblage Zone is commonly associated with the following mollusc genus within the areas to the south and north of the study area: Mytiloides and Morrowites. Furthermore, these dates constrain the Cenomanian–Turonian boundary, provide accurate chronostratigraphic markers for intra and interbasinal correlation and serve to strengthen global linkages to Ocean Anoxic Event 2 (OAE2) during the Greenhorn Cycle transgression.

First putative occurrence in the fossil record of choanoflagellates, the sister group of Metazoa

Choanoflagellates are microeukaryotes that inhabit freshwater and marine environments and have long been regarded as the closest living relatives of Metazoa. Knowledge on the evolution of choanoflagellates is key for the understanding of the ancestry of animals, and although molecular clock evidence suggests the appearance of choanoflagellates by late Neoproterozoic, no specimens of choanoflagellates are known to occur in the fossil record. Here the first putative occurrence of choanoflagellates in sediments from the Cretaceous (Cenomanian–Turonian) is described by means of several cutting-edge petrographic techniques, and a discussion of its paleoenvironmental significance is performed. Furthermore, their placement in the organic matter classification systems is argued, with a placement in the Zoomorph Subgroup (Palynomorph Group) of the dispersed organic matter classification system being proposed. Regarding the ICCP System 1994, incorporation of choanoflagellates is, at a first glance, straightforward within the liptinite group, but the definition of a new maceral may be necessary to accommodate the genetic origin of these organisms. While modern choanoflagellates may bring light to the cellular foundations of animal origins, this discovery may provide an older term of comparison to their extant specimens and provide guidelines for possible identification of these organic components in other locations and ages throughout the geological record.